Precipitation - water falls from clouds in various forms and is returned to land and sea.

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The Carbon Cycle

Carbon Dioxide in air. Plants use CO2 in photosynthesis to make carbohydrates, fats and proteins. Eating passes carbon compounds in plants to animals. Plants and animals respire, realising CO2 into air. Plants and animals die and decompose, or are turned into useful products. Broken down by decomposers which respire and realese CO2 into air. Useful products are burned (combustion) which releases CO2 into air.

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The Nitrogen Cycle

Atmosphere contains 78% N2, very unreactive so can't be used directly by plants and animals. Nitrogen is needed for making growth proteins.

Decomposers - break down proteins and urea and turn them into ammonia.

Nitrifying bacteria - turn ammonia in decaying matter to nitrates.

Nitogen-fixing bacteria - turn N2 into useful nitrogen compounds.

Denitrifying bacteria - turn nitrates to N2.

Lightning - can make nitrogen react with oxygen and make nitrates as there is so much energy.

Plants get nitrogen from soil. Animals get proteins by eating.

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Carbon Monoxide

Poisonous. If it combines with red blood cells it prevents them from carrying oxygen. Produced when fossil fuels burn without enough air. Released in car emissions. Modern cars have catalytic converters to turn CO into CO2.

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Sulfur Dioxide

Causes acid rain. Burning fossil fuels releases CO2 and SO2. SO2 comes from sulfur impurities in fossil fuels. When gas mixes with rain clouds it forms dilute H2SO4. Internal combustion engines in cars and power stations are the main cause of this.

It causes lakes to be more acidic. Organism can't survive acidic conditions and die. Kills trees. Damages leaves and releases toxic substances from soil so trees can't take up nutrients.

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Carbon Monoxide

Poisonous. If it combines with red blood cells it prevents them from carrying oxygen. Produced when fossil fuels burn without enough air. Released in car emissions. Modern cars have catalytic converters to turn CO into CO2.

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Greenhouse Gases

CO2 - released in car exhausts, industrial processes and burning fossil fuels. Deforestation affects the level of CO2 in atmosphere.

Methane - cattle rearing and rice growing.

Nitrous Oxide - fertiliser and vehicle engines.

CFCs - man made chemical in aerosal sprays and fridges. Powerful greenhouse gas and damages ozone layer. Countries don't use them any more. Leaks from old fridges.

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The Greenhouse Effect

Trap heat from sun. Without greenhouse gases it would be damn cold. Humans increasing greenhouse gases has an enhanced greenhouse effect. The earth is heating up and causes climate change. Causes changing crop growth of flowering when ice caps melt.

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Eutrphication

Fertilisers enter water and add extra nutrients. Algae grows fast and blocks out light. Plants can't photosynthesise and die. Microorganisms that feed on dead plants increase in number and deplete all the oxygen. Other organisms that need oxygen die.

Can also be caused by sewage. Sewage contains phosphates from detergents and nitrates from faeces.

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Deforestation

Leaching - trees take up nutrients from soil before they can be washed away by rain. They are returned when they did. Without trees nutrients get leached away and don't get replaced, leaving infertile soil.

Disturbing Water Cycle - trees stop rainwater reaching rivers too quickly. Without trees there is flooding. There is no transpiration so rainwater is not released into atmosphere so local climate is drier.

Disturbing Balance of CO2 and O2 - take in CO2 by photosynthesis, store it in wood and release it when they decompose. When trees burn they release all the CO2 at once. Fewer trees means less oxygen being released so oxygen levels go down.